Method for prepregging tackifier for cmc articles

ABSTRACT

A method of creating a tackified prepreg, includes steps of providing a fiber weave having unidirectional fibers and woven sections spaced apart from one another to provide unidirectional fiber sections, applying a tackifier to the fiber weave, arranging layers of the fiber weave onto one another to provide a stack, and wrapping the stack around a form to provide an article having a desired shape.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 15/022,015, filed on Mar. 15, 2016, which is a U.S. NationalPhase Application of International Application No. PCT/US2014/055199,filed on Sep. 11, 2014, which claims priority to U.S. ProvisionalApplication No. 61/878,994, filed on Sep. 17, 2013.

BACKGROUND

This disclosure relates to a method of manufacturing a gas turbineengine airfoil from a CMC.

Gas turbine engines typically include a compressor section, a combustorsection and a turbine section. During operation, air is pressurized inthe compressor section and is mixed with fuel and burned in thecombustor section to generate hot combustion gases. The hot combustiongases are communicated through the turbine section, which extractsenergy from the hot combustion gases to power the compressor section andother gas turbine engine loads.

Both the compressor and turbine sections may include alternating seriesof rotating blades and stationary vanes that extend into the core flowpath of the gas turbine engine. For example, in the turbine section,turbine blades rotate and extract energy from the hot combustion gasesthat are communicated along the core flow path of the gas turbineengine. The turbine vanes, which generally do not rotate, guide theairflow and prepare it for the next set of blades.

It is desirable to provide fiber-based articles for their lightweightand durability in high temperature applications. One example processwraps a resin impregnated ceramic matrix composite (CMC) cloth about amandrel to form an article to provide a desired shape. The article andresin are heated to high temperatures to pyrolyze the structure and forma crystalline ceramic metal matrix.

SUMMARY

In one exemplary embodiment, a method of creating a tackified prepreg,includes steps of providing a fiber weave having unidirectional fibersand woven sections spaced apart from one another to provideunidirectional fiber sections, applying a tackifier to the fiber weave,arranging layers of the fiber weave onto one another to provide a stack,and wrapping the stack around a form to provide an article having adesired shape.

In a further embodiment of the above, the method includes the step ofapplying a resin to the article in a mold.

In a further embodiment of any of the above, the resin is a liquid atroom temperature.

In a further embodiment of any of the above, the resin is aceramic-based.

In a further embodiment of any of the above, the tackifier and resin aresilicon carbide-based.

In a further embodiment of any of the above, the method includes thestep of heating and curing the article.

In a further embodiment of any of the above, the method includes thestep of machining the cured article.

In a further embodiment of any of the above, the method includes thestep of pyrolyzing the article, including the tackifier and the resin,subsequent to the machining step.

In another exemplary embodiment, a CMC article for a gas turbine engineincludes a wall that has multiple tacks joined to one another. Eachstack includes multiple layers. The layers consist of unidirectionalfibers that form a ceramic matrix composite with a resin and a tackifierthat are different than one another.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be further understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 is a flow chart of an example method of manufacturing a CMCarticle.

FIG. 2 is a schematic view of a prepregging process.

FIG. 3 is a side view of the prepregging process shown in FIG. 2.

FIG. 4 is a schematic view of multiple layers of fiber material kittedinto stacks.

FIG. 5 is an example cross-sectional view of the stacks wrapped about amandrel providing an article having a desired shape.

The embodiments, examples and alternatives of the preceding paragraphs,the claims, or the following description and drawings, including any oftheir various aspects or respective individual features, may be takenindependently or in any combination. Features described in connectionwith one embodiment are applicable to all embodiments, unless suchfeatures are incompatible.

DETAILED DESCRIPTION

Referring to FIG. 1, a method 10 is disclosed of manufacturing ceramicmatrix composite (CMC) articles. The method 10 includes prepregging aCMC fiber weave that includes unidirectional fiber sections with atackifier, as indicated at block 12. Referring to FIG. 2, the fiberweave 28 includes unidirectional fibers 30 woven with cross fibers 32 toprovide spaced apart woven sections 34. Unidirectional fiber sections 38are provided between the woven sections 34. The woven sections 34provide stability to the unidirectional fibers 30 during the prepreggingprocess to hold the unidirectional fibers 30 in alignment with oneanother during the tackifying process. The fiber weave 28 is fed throughrollers, for example, first and second rollers 42, 44 with theunidirectional fibers 30 oriented in a same direction as a feeddirection F of the rollers 42, 44.

Referring to FIG. 3, the tackifier 40 may be applied to the fiber weave28 in a bath. The second rollers 44 are arranged with respect to oneanother to provide a desired thickness 46 of the tackified fiber weave.Once the fiber weave 28 has been tackified, the unidirectional fibers 30in the unidirectional sections 38 may be separated from the wovensections 34 at cut lines 36 shown in FIG. 2 (block 14 in FIG. 1). Theunidirectional fibers 30 are sufficiently adhered to one another withthe tackifier, such that they can be handled and trimmed without fallingapart or frying the tow.

In one example, the tackifier is a pre-ceramic polymer material, forexample, a silicon carbide. The tackifier is melt processable polymersolid at room temperature, for example, an amorphous solid that readilyflows at moderate temperatures. In order to not compromise the integrityof the CMC, a tackifier was chosen that has the same chemical backboneas the matrix that material used, polycarbosilane. Upon pyrolyzing ofthe tackifier it is incorporated into the matrix of the CMC. Thetackifier can also be loaded with filler particles to aid in processingin addition to altering desired CMC properties.

The degree of “tack” that is provided by the tackifier enables thelayers of the unidirectional fibers 38 to be kitted and stuck to oneanother to produce stacks 50, as shown in FIG. 4 (block 16 in FIG. 1).The layers 48 are sufficiently sticky such that the layers will stick toone another at room temperature using hand pressure only or low levelsof heat.

The tackifier process will provide the fabric/fiber to which it isapplied with the appropriate handling characteristics that allow thefabric to be cut, handled and kitted while maintaining edge, plyintegrity and fiber alignment. The fabric/fiber can then be utilized inRTM processing of complex shapes while maintaining handlingcharacteristics. This process is suitable for the processing ofunidirectional fiber tows.

Returning to FIG. 1, block 18, the stacks 50 are wrapped about a form52, such as a mandrel shown in FIG. 5, to provide an article 54 having adesired shape. With continuing reference to FIG. 1, the article isarranged into a mold and a pre-ceramic polymer resin is injected intothe mold. The resin and tackifier are different than one another. In oneexample, the resin is a liquid at room temperature. In one example, thetackifier has a greater carbon content than the resin.

The article is heated within the mold, as indicated at block 20. Thearticle is allowed to cool and cure, enabling the resin and tackifier toset and the article to sufficiently take its shape for subsequenthandling, as indicated at block 22. The article then may be machined toa finished shape, as indicated at block 24. Finally, the article may bearranged in a fixture to maintain its shape and heated to hightemperatures, for example, 1000-1600° C., to pyrolized the articleincluding the tackifier and resin, to form a crystalline ceramic matrixcomposite. The CMC article includes multiple stacks, each havingmultiple layers. The layers consist of unidirectional fibers that form aceramic matrix composite with the resin and the tackifier.

It should also be understood that although a particular componentarrangement is disclosed in the illustrated embodiment, otherarrangements will benefit herefrom. Although particular step sequencesare shown, described, and claimed, it should be understood that stepsmay be performed in any order, separated or combined unless otherwiseindicated and will still benefit from the present invention.

Although the different examples have specific components shown in theillustrations, embodiments of this invention are not limited to thoseparticular combinations. It is possible to use some of the components orfeatures from one of the examples in combination with features orcomponents from another one of the examples.

Although example embodiments have been disclosed, a worker of ordinaryskill in this art would recognize that certain modifications would comewithin the scope of the claims. For that and other reasons, thefollowing claims should be studied to determine their true scope andcontent.

What is claimed is:
 1. A method of creating a tackified prepreg,comprising steps of: providing a fiber weave having unidirectionalfibers and woven sections spaced apart from one another to provideunidirectional fiber sections; applying a tackifier to the fiber weave;arranging layers of the fiber weave onto one another to provide a stack;and wrapping the stack around a form to provide an article having adesired shape.
 2. The method according to claim 1, comprising the stepof applying a resin to the article in a mold.
 3. The method according toclaim 2, wherein the resin is a liquid at room temperature.
 4. Themethod according to claim 3, wherein the resin is a ceramic-based. 5.The method according to claim 4, wherein the tackifier and resin aresilicon carbide-based.
 6. The method according to claim 1, comprisingheating and curing the article.
 7. The method according to claim 6,comprising the step of machining the cured article.
 8. The methodaccording to claim 7, comprising the step of pyrolyzing the article,including the tackifier and the resin, subsequent to the machining step.9. A CMC article for a gas turbine engine comprising: a wall havingmultiple tacks joined to one another, each stack including multiplelayers, wherein the layers consist of unidirectional fibers forming aceramic matrix composite with a resin and a tackifier that are differentthan one another.